Generally, a flash memory device is a nonvolatile semiconductor memory device capable of electrically performing program and erase operations. The flash memory device exhibits properties of high capacity and high speed when used in applications such as storage devices or code memories or mobile devices. The flash memory device may be classified as a NAND type flash memory or NOR type flash memory. The cell array of the NOR type flash memory device has a structure where a plurality of memory cells are connected in parallel to one bit line. In contrast, the NAND type flash memory has a structure where a plurality of memory cells are connected in series to one bit line.
The NOR type flash memory device stores codes for controlling internal operations. Accordingly, the NOR type flash memory device reads stored codes and uses the stored codes to perform controlling of write, read, and verify operations. The NOR type flash memory device controls various kinds of operations based on the code read. In some cases, a time delay may occur.
The NOR type flash memory device performs a verify read operation between code reading operations. The NOR type flash memory device supplies a voltage to a memory cell in order to perform a verify read operation. The NOR type flash memory device requires a setup time (time for charging a memory cell voltage due from a voltage supply) and a recovery time (time for recovering a memory cell voltage). Accordingly, in the NOR type flash memory, time delay occurs because of the setup time and the recovery time during a verify operation. Moreover, the NOR type flash memory performs a code reading operation through a normal read operation and then performs a verify operation in the next step such that continuous read verify operations are impossible. In the NOR type flash memory, memory cells for performing a read operation are distinguished from memory cells for performing code reading operations. Therefore, in order to perform a verify operation during a read operation, a code reading operation needs to be performed using additional memory cells instead of memory cells where data are stored. As a result, time delay occurs because of a code reading operation in the NOR type flash memory.